The present invention refers to a differential pinion assembly, especially suitable for use in a motor-vehicle transmission, having a simple and very compact structure and where the friction between the relative movement members is substantially a rolling friction.
The differential units for motor-vehicles are adapted to transmit the movement from the driving shaft to the two axleshafts and notoriously comprise a box in the inside of which rotates a differential carrier actuated by a toothed driving pinion engaging with a crown gear solid with the differential carrier. The differential carrier is supported during rotation on the box by means of a pair of antifriction bearings, usually taper roller bearings onto which the radial and axial loads applied to the differential carrier by the pinion are discharged. Inside the differential carrier are located satellite gears, rotatable relative to the same and mating with two planetary gears with each of which an axle shaft is solid. The aforesaid satellite and planetary gears are normally rotatable with sliding friction, the former round a pin located inside the differential carrier, the latter in appropriate seats of the differential carrier. The driving toothed pinion is solid with a shaft, this too supported by a pair of antifriction bearings, normally taper roller bearings, and transmission of the movement from the driving shaft to the latter shaft takes place by means of two flange half-couplings, one of which, fitted with a splined hub, mates with the pinion shaft.
The differential units of the above described type show some inconveniences.
First of all, their structure is rather complex, and their assembling and disassembling involves lengthy and delicate operations. In effect, since for supporting the differential carrier and the pinion shaft normal antifriction bearings are used, when fitting these special measures and precautions are to be taken, and seats, shoulders, locking and adjusting elements as well as other parts of like kind must be provided. Moreover, the relative movement between some parts of the unit, for instance between the planetary gears and the differential carrier is pure sliding movement, with rather high friction values. Lastly, during operation unbalancing centrifugal forces may arise due to the presence of eccentricity in the fitting of the two above mentioned half-couplings that connect the transmission shaft and the unit.